UNIX for Dummies Questions & Answers

Sorry I meant the regular expression from my code above.

It almost works but as soon as I add the ? it no longer picks up the numbers 1.1, 1.2 etc as valid. If I dont have the question mark things seem to work but it wont except just a single digit as a valid version number which is what I want. Some examples of what I want valid are below as well as the latest code.

Code:

1 valid
1.1 valid
1.12 valid
12.1 valid
1...1 invalid
1a invalid
1.1a invalid

Code:

while true
do
        print -- "Please enter the version number"
        read version
        echo "${version}" |grep "^[0-9]*\.?[0-9]$" >/dev/null
        if [[ $? != 0 ]]
                then
                print -- "Version is not a number"
        else
        break
        fi
done

Sorry, you should use \? in BRE. Otheriwse use grep -E/egrep.
From the manual pages of grep:

Sorry, I still get the same result.

OK, some grep implementations support only limited regular expressions (/usr/bin/grep on Solaris, for example),
but .? (note, there is no backslash before the ?) should work with egrep.
Did you try it?

Brilliant, this has done the trick. Thanks so much for your help. Maybe in 20 years I might have learnt all these differences but probaly not

As you see, I'm using shell scripting every day but I often forget the details too